Immunopharmacology of ulipristal as an emergency contraceptive.

摘要: A new progesterone antagonist, ulipristal has been made available as an emergency contraceptive. Ulipristal's major mechanism of action contraceptive ascribed to its ability delay ovulation beyond the life span sperm. This paper analyzes potential (1) when unprotected intercourse and administration occur outside fertility window (2) at or within 24 hours ovulation. When use a single low dose window, behaves like placebo. but before ovulation, by delaying thereby preventing fertilization. then abortifacient action. It is proposed that taken after fertilization implantation due block maternal innate immune system become immunotolerant paternal allogenic embryo. Progesterone's critical actions involving early pregnancy factor, progesterone-induced blocking uterine natural killer cells are compromised ulipristal.